The present invention relates to a dispenser, especially a hand-held spray dispenser in which a spray is emitted upon manual actuation of a valve.
For many years spray dispensers for dispensing products such as hair spray, deodorants, room air fresheners, etc., have utilized a container in which the product is stored in liquid form. A propellant gas under pressure occupies a head space between the top of the container and the liquid product. A dip tube extends downwardly through the propellant and product from a discharge valve located at the top of the container. When a user opens the discharge valve, the propellant pushes the liquid product into the bottom of the dip tube and then upwardly through the dip tube to the valve.
Propellant gases which have commonly been used have included butane and pentane, for example. Those gases feature the ability to become dissolved within the liquid product under the usual pressure conditions occurring within the container. Hence, the product is discharged in the form of liquid particles mixed with bubbles of the propellant gas. When exposed to the lower atmospheric pressure, those bubbles expand suddenly to advantageously break up the liquid particles into a finer spray pattern.
In some cases, the valve is configured to mix additional propellant gas directly from the head space to the product during discharge in order to create yet a finer spray pattern.
The conventional propellant gases have exhibited ideal product-expelling characteristics, i.e., an essentially constant pressure of a specified magnitude which can be maintained continuously for a specified duration of time.
More recently, however, due to concerns about environmental pollution, conventional propellant gases have fallen into disfavor. Alternative sources of propulsion have been sought which will satisfy the above-mentioned product-expelling characteristics without being accompanied by the discharge of polluting gases.
Dispensers have heretofore been proposed which employ an internal energy-storing member capable of being mechanically compressed by a rotatable actuator to pressurize a liquid product, e.g., see U.S. Pat. No. 3,195,168 which proposes to use an energy-storing member in the form of a coil spring. However, coil springs are not ideally suited to continuously produce a constant pressure for a sufficiently long duration to satisfy most spraying requirements.
In Williams U.S. Pat. No. 5,042,696 a multipiece piston is disclosed which comprises a product ejecting member and an energizing member separated by a gas-filled space. The energizing member is raisable by rotation of an outer sleeve to compress the gas while pressurizing the product, which is located above the ejecting member. The compressed gas acts as a gas spring to store energy. That energy is gradually released to eject the product when a discharge valve is opened by a user. Once the gas pressure has been dissipated, the outer sleeve is rotated to recompress the gas. This mechanism has been shown to provide a generally uniform pressure which can be maintained continuously at a sufficiently high magnitude for a suitable duration. However, in certain instances there exists a tendency for the gas to migrate through the container wall (especially if the wall is formed of certain plastics), thereby shortening the shelf-life of the dispenser. In such instances, it would be necessary to enclose the air within a collapsible bellows, but the possibility of leakage and resultant pressure loss might still exist.
It would, therefore, be desirable to provide a dispenser with an energy storing mechanism able to produce an essentially constant pressure that can be maintained continuously at a sufficiently high magnitude for a suitable duration, and which exhibits an ample shelf life.
It would also be desirable to ensure that a user of a dispenser having a manually actuable energy-storing member cannot accidentally over-pressurize that member.
Furthermore, it would be desirable to minimize the amount of disposable waste created when a dispenser has been emptied of its product.